This application claims the priority of Korean Patent Application No. 2002-27068, filed May 16, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a transparent conductive layer composition, and more particularly, to a transparent conductive layer composition having anti-reflective and electromagnetic wave-shielding properties, a transparent conductive layer formed of the composition, and an image display having a front panel formed by coating the transparent conductive layer.
2. Description of the Related Art
In the prior art, an anti-static, anti-reflective, thin transparent layer for reducing electric charges and reflection has been coated on a transparent display panel of a cathode ray tube (CRT), a vacuum fluorescent display (VFD), or a liquid crystal display (LCD).
The growing concern over effects of electromagnetic waves on the human body necessitates shielding electromagnetic waves and an electromagnetic field produced therefrom as well as the anti-static function in display devices. As an example, when a thin conductive layer for shielding electromagnetic waves is formed on a panel surface of a display, for example, a CRT, the sheet resistance of the electromagnetic wave-shielding conductive layer should be as low as 102-104 Ω/cm2, while an antistatic conductive layer needs a sheet resistance of about 107 Ω/cm2.
When a coating composition containing conductive oxide, such as antimony-doped tin oxide or tin-doped indium oxide, is applied to form a thin conductive layer having a low sheet resistance, the thickness of the thin conductive layer should be greater than conventional conductive layers. In this case, the anti-reflective function cannot be expected from the thin conductive layer. Accordingly, it is impractical to form an electromagnetic wave-shielding and anti-reflective conductive layer using a conductive oxide such as the antimony-doped tin oxide and tin-doped indium oxide.
In another method for forming a low sheet resistance thin conductive layer, a conductive layer coating composition containing metal micro-particles, such as silver micro-particles, is applied to the surface of a substrate. In this method, in order to improve the dispersion properties of the metal micro-particles, an organic stabilizer, such as polyvinyl alcohol, polyvinyl pyrrolidone gelatin, is incorporated into the thin conductive layer coating composition.
However, due to the organic stabilizer used in the thin conductive layer coating composition, the metal micro-particles become close and interact in the thin conductive layer, thereby increasing grain boundary resistance. As a result, the sheet resistance of the conductive layer cannot be lowered. For this reason, it is required to decompose and remove the organic stabilizer from the conductive layer by heating at a high temperature of about 400° C.
However, heating the conductive layer at such a high temperature in order to decompose and remove the organic stabilizer causes the metal micro-particles to dissolve and agglomerate, thereby degrading the transparency of the thin conductive layer. In particular, if the transparent conductive layer contains silver micro-particles, the metal micro-particles grow due to the oxidization and ionization of the metal, and the thin conductive layer corrodes, thereby lowering the conductivity and light transmittance of the thin conductive layer. Therefore, the performance of an image display having the conductive layer is unreliable.
A solution, suggested by Korean Laid-open Patent Publication No. 98-25037, uses a transparent conductive layer containing composite metal micro-particles having an average particle diameter of 1-200 nm on a substrate and a transparent coating layer on the transparent conductive particle layer, which has a refractive index smaller than the transparent conductive layer.
However, this transparent conductive layer has problems in practical use since the metal micro-particles in the transparent conductive layer is oxidized due to moisture or oxygen in the air. In addition, the use of expensive metal micro-particles increases the manufacturing cost of the transparent conductive layer. Further, the properties of the transparent conductive layer associated with the sheet resistance need improvement.